Romney tops field in Iowa, while Gingrich slides

Former Massachusetts Gov. Mitt Romney may well be the emerging front-runner heading into Tuesday's Iowa caucuses, according to a new poll of Hawkeye State Republicans likely to participate in the contest.

Romney enjoys a slight advantage over Texas Rep. Ron Paul, according to a CNN/TIME poll released Wednesday; former House Speaker Newt Gingrich, who's been pummeled by ads in the state, has fallen to fourth -- behind former Pennsylvania Sen. Rick Santorum.

Romney also enjoys a commanding lead over other Republican candidates in New Hampshire.

Twenty-five percent of likely caucus-goers said they would choose Romney. Paul was the choice of 22 percent, while 16 percent named Santorum, and 14 percent named Gingrich. Eleven percent said they would support Texas Gov. Rick Perry, and nine percent back Minnesota Rep. Michele Bachmann, the winner of August's straw poll.

Former Utah Gov. Jon Huntsman, who's not competing in the state, ranks as the choice of one percent of Iowa Republicans.

The polls reflect shifting political terrain in Iowa since the release of polls earlier this month, which showed Gingrich ahead of his GOP challengers in Iowa. An NBC News-Marist poll released Dec. 4 found Gingrich leading as the preference of 21 percent of likely caucus-goers, followed by Romney at 18 percent and Paul at 17 percent. The Des Moines Register's Iowa poll showed similar results.

(A new NBC News-Marist poll of the Iowa caucuses will be released later this week.)

In the intervening weeks, the different candidates -- along with super PACs acting on their behalf -- have spent millions on ads in the state. Arguably the most significant expenditures have been made by Restore our Future, a pro-Romney super PAC that has run ads castigating Gingrich, and the Paul campaign, which has also spent to promote the libertarian-minded candidate, and in opposition to Romney and Gingrich.

Santorum has also been the beneficiary of increased social conservative suppoprt, most notably from Bob Vander Plaats, the head of The Family Leader, who endorsed the former senator independent of his group.

The new figures also underscore the fluidity of the GOP field ahead of the Jan. 3 caucus. Gingrich has slid over the past month just as Herman Cain and Bachmann -- who had each led in Iowa at one point -- had faded. The poll points to the possibility of even more shifting in the final days of the Iowa campaign: 54 percent of likely caucus-goers said they will definitely support the candidate they named, but 43 percent said they might change their mind.

Once Iowa's contest is decided, the candidates will head to New Hampshire, the host of the nation's first primary and the cycle's second nominating contest.

Forty-four percent of likely Republican primary voters in New Hampshire said they would back Romney. Paul places second, at 17 percent, followed by Gingrich at 16 percent, Huntsman at nine percent, Santorum at four percent, Bachmann at three percent and Perry at two percent.

Fifty-one percent of New Hampshire primary voters said they've made up their mind, while 45 percent said they may change their mind -- offering hope to the winner of Iowa's caucuses to use a win there as a springboard heading into the Granite State.

The polls, conducted Dec. 21-24 and Dec. 26-27 by ORC, have a 4.5 percent margin of error for the Iowa results, and a four percent margin of error for the New Hampshire results.